Here is a picture of my dead duck. It was stiff as well, but I eventually stretched its wings out enough to snap a couple shots. I believe the contrasting colors are what looks most odd about the duck in question. I look at the image again, and I see what looks like a wing that doesn't match the body, but I think only because those two colors don't match (body and wing). If the duck was on its belly, it would look similar to the image I'm posting. The wing in question can be best described like this: Take your arm and tuck your elbow to your side, and raise your forearms up, and if the human body could contort, you would touch your wrist (where your radius and ulna meet) to your shoulder, and if the human body could contort like a duck, you would bend your wrist downward, and point your fingers (primaries) downward. That is what you see with the first duck. Add to that, that the duck is on its side and you have contrasting colors, it sort of looks detached. Now stretch that wing because there is also a large bone called a humerus that is running right about even to that radius and ulna (again ducks are built a bit differently than us humans), and you'll see the flight web is actually attached right at the point of that same wing where the coverts lay (in the image it is the point that resembles a shoulder when in fact it's the wrist that is making contact with the bird's breast/neck juncture). The rest of the wing (humerus and flight web) is not stretched out like the image I am posting.
In other words it is an optical illusion, but it certainly looks like it is part of the duck in question. Most importantly, what does someone have to gain by removing a wing from a body, and placing it near the body of another duck, when both ducks (wing and yes body) are obviously leucistic? It would take two leucistic mallards to pull off that trick!?